Do this mod at your own risk! Soldering together lithium-ion batteries can be dangerous especially if you short them out. Those without soldering skills probably shouldn't do this! This can also destroy your phone!

Step One- Gather materials and prepare a clean working area so you have ample room

Step Two- Charge both NEW batteries fully so their voltages are about the same.

Step Three - Place one battery in phone and put rolled up tape or double sided tape between back case and battery close it tight

Step Four - Remove back case so the battery comes out with it mark it with a pencil or marker

Step Five - Cut out back piece with razor knife or rotary cutting tool be careful not to break the back case. Keep the thin plastic we will use that later

Step Six - place the rubber piece on with nothing else and cut out the hole by pressing on it to mark the battery compartment and cut the rubber with the razor knife.

Step Seven - Tape both batteries together and place them in the phone put on the back case and the rubber. Place double sided tape on battery then line up the hard ULAK case with the rubber. Once alligned press them firmly together and pull the hard ULAK case off with the battery still attached. Mark where the batteries are with something. Remove the batteries and use the rotary cutting tool to cut the square battery hole out.

Step Eight - Clean up all the holes so that each piece can be removed without interfering with the batteries.

Step Nine- Use the liquid tape on the P769 back cover where the copper might be exposed

Step Ten - Solder positive to positive then check for shorts if there are no shorts solder negative to negative and check for shorts. if there are no shorts and the connections are good and sturdy then all the soldering is done. Make sure that the wire doesn't stick out to far from the battery because it might not fit in the battery compartment. To make things easier I burnt away the little bit of plastic that sticks up between the solder bridge and it is also a good idea to tin the connections and the wire before soldering them together.

Step Eleven - Once all the soldering is done and you are certain there are no shorts and your connections are good. connect the battery to the phone and try to turn it on. It should boot up with around 100% battery life during the first hour of use make sure to feel for battery warmth. If it starts to get really hot. It's probably messed up and you should fix it. Once all the checks are done and the battery fits in the phone fine use fast discharge and turn it on select everything if you want. Run it for about 5 or 10 minutes. if the battery gets warm but the temperature monitor doesn't move than your solder bridges are too tall making the other two connections not to touch the pins inside the battery compartment. After that is done and working use the liquid tape to cover the exposed connections that don't go inside your phone.

Step Twelve - Put the all the case pieces back on. Take the piece that you cut off the P769 back case and place it ontop of the battery use tape to tape it on. Then put on any decorative tape to cover the ugly hole. Take off the ULAK hard plastic case and put tape on the other side to prevent it slightly sticking to the battery. Then you can put it back together and enjoy you're long battery life.

Yeah it's a pretty good mod. I love absolutely love it. feels good in my hand, it isn't heavy. it really isn't hard to do as long as you have the tools and take your time. I love it. idt i've had my phone die in one day since I have did the double battery mod. it's quite spectacular. I suppose I have the extra battery life because it's a bit undervolted by AntonX's CM 11.

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